A. Field of the Invention
The present invention relates to sealant compositions for bonding surfaces together. More particularly, the present invention relates to anaerobic sealant compositions which polymerize in the absence of oxygen to bond adjacent surfaces together when the surfaces are joined to the exclusion of oxygen. The particular monomers disclosed herein polymerize in the absence of air to deliver virtually full strength at temperatures in the range of about 250.degree.-400.degree. F. and are reactive to practically all metal surfaces.
B. Prior Art
It is known to employ "anaerobic" sealant compositions which polymerize in the absence of oxygen for the purpose of bonding two surfaces together and especially for bonding metal surfaces such as in bonding a nut to a bolt. The anaerobic sealant composition is coated on at least one of the surfaces and when the two surfaces are joined to exclude oxygen therebetween, the monomer of the composition polymerizes and cures to strongly bond the surfaces together. A suitable monomer for the purpose of bonding should have a polymerization rate of less than about 1 hour when oxygen is excluded from the monomer as set forth in the Burnett et al. U.S. Pat. No. 2,628,178. It is therefore conventional to include within an anaerobic sealant composition a polymerization catalyst for the purpose of speeding up the polymerization process of the monomer once oxygen has been excluded.
It is also necessary that the sealant composition be shelf-stable and in this regard it is desirable that the monomer will not polymerize or gell for periods of time as long as 1 year or more. It is therefore common to include within an anaerobic sealant composition a polymerization inhibitor for storage.
The following patents relate to anaerobic sealant compositions containing, in addition to other components, a monomer having the general formula EQU CH.sub.2 =CR-COO[(CH.sub.2).sub.m (CHR").sub.p CHR-O].sub.n CO-CR'=CH.sub.2
where R is a member selected from the class consisting of hydrogen, --CH.sub.3, --C.sub.2 H.sub.5, --CH.sub.2 OH, and --CH.sub.2 --O--CO--CR'=CH.sub.2 radicals; R' is hydrogen, chlorine, methyl or ethyl; R" is a member selected from the class consisting of hydrogen, --OH radical, and --O-- CO--CR'=CH.sub.2 radical; m is an integer equal to at least 1, e.g., from 1 to 3, or higher, for instance, from 1 to 4, inclusive; n is an integer equal to at least 2, for example, from 2 to 20 or more, and p is 0 or 1: Burnett U.S. Pat. No. 2,628,178; Krieble U.S. Pat. No. 2,895,950; Krieble 3,041,322; Krieble U.S. Pat. No. 3,043,820; Krieble U.S. Pat. No. 3,046,262; Krieble U.S. Pat. No. 3,218,305; Krieble U.S. Pat. No. 3,203,941; Gorman et al. U.S. Pat. No. 3,300,547; Nordlander U.S. Pat. No. 3,435,012; Krieble U.S. Pat. No. 3,489,599; Frauenglass U.S. Pat. No. 3,547,851; Toback U.S. Pat. No. 3,591,438; Toback U.S. Pat. No. 3,616,040; Frauenglass U.S. Pat. No. 3,625,875; Toback U.S. Pat. No. 3,625,930; Hauser U.S. Pat. No. 3,634,379; Newmann U.S. Pat. No. 3,672,942.
Another monomer useful in anaerobic sealant compositions is an acrylic ester of an alkylaminoalkyl alcohol, as disclosed in Rai et al. U.S. Pat. No. 3,493,552. Monomeric polyacrylate esters formed by the reaction of a monofunctional, acrylate terminated material with an organic polyisocyanate are disclosed as useful monomers for anaerobic sealant compositions in the Gorman et al. U.S. Pat. No. 3,425,988.